Multi-Sheet Designs on proteus-7.8
It is increasingly common in larger designs to split the schematic into multiple sheets. This serves both to reduce clutter on the schematic and also to organize the design into logical blocks. ISIS fully supports this methodology and we have arranged our tutorial design into two sheets in order to cover the relevant procedures. The work we have done so far has been to complete the first sheet (processor, sensors and memory circuitry), meaning we still need to cover the analog and power circuitry. We’ll do this on a separate sheet.
Adding Sheets to a Design
To add a new sheet to the schematic we simply invoke the command from the Design menu as shown below.
Try this now to generate the second sheet.
Naming, Ordering and Navigating Sheets
Before we lay out the circuitry on this sheet we need to do a little housekeeping. While it’s not necessary it is often helpful to name the different sheets on the schematic and also to order them in some sensible fashion. We can do both of these things via the Edit Sheet Properties command on the Design Menu.
The Sheet Title is what will be displayed and should therefore reflect the contents of the sheet. In our case let’s name it ‘Analog, Reference & Power’.
Sheets on the schematic are organized by Sheet Name and by default these are ROOT10, ROOT30 and so on. A sheet with name ROOT30 will therefore appear behind the first sheet (default name ROOT10). If you prefer purely numeric nomenclature we can change the sheet name to be ‘2’, to better reflect it’s position in the design structure.
The default sheet names may seem inconsistent. This is because ISIS also has a Master Sheet, present in all designs, which allows the application of a company logo, revision number, author and other schematic information. This is beyond the scope of this tutorial but more information can be found in the Templates chapter of the accompanying reference manual (Help Menu – ISIS Help).
Sometimes, it is desirable to have a base annotation for a sheet; this means that the global annotator will increment from the value entered in this field. For example, if we set this to be 100 then the first resistor placed on the sheet would be annotated as R100. When left at it’s default value the global annotation will continue from it’s current position – this is fine for the purposes of the tutorial.
Before exiting, your dialogue form should now look something like the following:
For completeness we should also follow this process for the sheet we have just finished laying out. Before we can change the properties of a sheet we must first navigate to that sheet in the design and ISIS provides several ways to do this :
- From the Design Menu select Root Sheet 2 at the bottom of the menu,
- From the Design Menu, select the Goto Sheet command, select the sheet and click OK to switch to that sheet.
- Use the PGUP and PGDOWN keyboard shortcuts to navigate between sheets. These cycle up and down the sheets respectively, although for a two sheet design they will seem to have the same function!
The Design Explorer is also a powerful way to navigate the schematic – this is covered in the Design Verification section of the tutorial and in more depth in the reference manual.
Once you find yourself back on the sheet we have laid out simply repeat the process above, with a sheet title of ‘MCU, sensors and memory’ and a sheet name of ‘1’.
You should now see correctly organized and labeled sheets at the bottom of the Design Menu,
Sheet Titles are shown in the Design Menu
Connectivity Between Sheets
Now that we have taken care of the naming, let’s navigate back to our blank sheet and lay out the analog circuitry. The following screenshot shows the circuit we need to draw.
As we can see, there are three logical blocks of circuitry; a reference generator for the ADC module, an analog buffer for the pressure channel and a DC/DC converter to provide 5V from the 3V battery to the other two sections on each pressure sampling time.
If you feel that you need more practice then you can use all of the techniques we have covered so far to complete the schematic. Alternatively, if you are comfortable with the basics of schematic entry we will load a pre-supplied completed schematic in the next section. Regardless, there are a couple of points of note that are worth emphasizing.
Firstly, connectivity between sheets is achieved by having terminals with the same name on both sheets. From the screenshot above you can see the named terminals and, switching to the first sheet, the corresponding terminals with the same name. This technique allows signals to propagate not only across a sheet but also across sheets.
Secondly, it is possible when placing wires to ‘guide’ the wire placement as you place the wire. This is achieved by left clicking the mouse as you change direction, placing an ‘anchor’ to help the follow-me algorithm place the wire the way you want. Typically, this is useful on more complex wire trails but we can look at a simple example for the purposes of illustration.
Consider the connection between the negative input of U4:B and resistor R18 as shown below.
If we delete this wire (right click and select delete), we could replace the connection in the usual way and the follow-me algorithm would make a decent job of it. However, if we wanted to be more precise we could proceed as follows:
- Hover the mouse over the negative input such that it turns green and then left click to start wire placement.
- Move the mouse along to the left and then left click the mouse once to place an ‘anchor’.
- Move the mouse up, left click to place an anchor, then right, left click to place an ‘anchor’ and finally down onto the wire between the op-amp output and resistor.
This technique constrains the follow-me algorithm and provides greater control during wire placement. If at any time during placement you change your mind and wish to remove an anchor simple right click the mouse once. Finally, if you want to completely disable the wire-auto-router and, for example, place a wire at 45 degrees, simply hold the CTRL button down on your keyboard during placement.
#collected from the proteus>>help>> tutorial page
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